Section 671 - Contracts for improvements; competitive bids(a) The commission shall proceed to arrange for the contracts for the required improvements. The letting of contracts for improvements shall be upon a competitive basis pursuant to public advertisement of the intention of the county government to receive sealed proposals for the work on said improvements. All contracts shall be entered into and acquisitions shall be made by the county government.(b) It shall be a term of each contract that 10 percent of all payments due shall be withheld until final certification by the commission that the work has been satisfactorily completed, in compliance with the contract.9 Del. C. 1953, § 671; 49 Del. Laws, c. 112, § 1; 57 Del. Laws, c. 762, § 4B.;